The process of Refractive eye surgery
Refractive eye surgery is any eye surgery used to improve the refractive state of the eye and decrease dependency on glasses or contact lenses. This can include various methods of surgical remodelling of the cornea or cataract surgery. The most common methods today use excimer lasers to reshape curvature of the cornea. Successful refractive eye surgery can help to reduce common vision disorders such as myopia, hyperopia and astigmatism.
Consists in cutting a flap of varying thicknesses in the cornea in order to access the tissue underneath. Surface treatment ablation has gained a renewed interest in recent years as evidence of good outcomes have been shown. These techniques are mostly effective for nearsightedness.
Automated lamellar keratoplasty (ALK): The surgeon uses an instrument called a microkeratome to cut a thin flap of the corneal tissue. The flap is lifted like a hinged door, targeted tissue is removed from the corneal stroma, again with the microkeratome, and then the flap is replaced.
Laser Assisted In-Situ Keratomileusis (LASIK): The surgeon uses a microkeratome to cut a flap of the corneal tissue (usually with a thickness of 100-180 microns). The flap is lifted
like a hinged door, but in contrast to ALK, the targeted tissue is removed from the corneal stroma with an excimer laser.The flap is subsequently replaced. One improvement over regular LASIK is the use of a femtosecond Laser to create the flap – this type is called IntraLasik, and can provide more precision, and therefore better results.
Laser Assisted Sub-Epithelium Keratomileusis (LASEK) is a procedure that also changes the shape of the cornea using an excimer laser to ablate the tissue from the corneal stroma, under the corneal epithelium, which is kept mostly intact to act as a natural bandage. The surgeon uses an alchohol solution to loosen then lift a thin layer of the epithelium with a trephine blade (usually with a thickness of 50 microns).  During the weeks or months following LASEK, the epithelium heals, leaving no permanent flap in the cornea. This healing process can involve discomfort comparable to that with PRK.
EPI-LASIK is a new technique similar to LASEK, that uses an epi-keratome (rather than a trephine blade and alcohol) to remove the top layer of the epithelium (usually with thickness of 50 microns). For some people it can provide better results than regular LASEK in that it avoids the possibility of negative effects from the alcohol, and recovery may involve less discomfort.
Photorefractive keratectomy (PRK) is an outpatient procedure generally performed with local anesthetic eye drops (as with LASIK/LASEK) . It is a type of refractive surgery which reshapes the cornea by destroying microscopic amounts of tissue from corneal stroma, using the computer-controlled beam of light (an excimer laser). The difference from LASIK is that the epithelium is removed (and a bandage contact lens must be used), and no flap is created. Recovery time is longer with PRK than with LASIK, though the final outcome (after 3 months) is about the same (very good). More recently, customized ablation have been performed with LASIK, LASEK, and PRK.